This invention relates to porometers and methods of stomatal measurement.
In one class of porometer, called a steady-state diffusion porometer, the moisture in a cuvette is measured and a dry gas is forced through the cuvette to maintain the moisture constant. A leaf in the cuvette has its transpiration and diffusion resistance measured by measuring the flow of air and the water vapor density of water in the chamber, using known formulae. Water vapor density is determined from temperature and moisture.
It has also been proposed to use a more refined formula for diffusion resistance in which the water vapor density within the leaf and the water vapor density in the chamber are both measured.
In the prior art instruments of this class, the rate of flow of the dry gas is manually adjusted and a meter measures the rate of flow. This instrument has a disadvantage in that it only measures the temperature and moisture in the chamber and does not measure the temperature of the leaf so that it is in error in certain ranges. Moreover, it cannot adjust instantaneously to changes of vapor pressure so that its calculations are in error at times because of sudden changes in the leaf.
Accordingly, it is an object of the invention to provide a novel porometer.
It is a further object of the invention to provide a novel method for measuring stomatal characteristics of plants.
It is a still further object of the invention to provide a novel flow meter for use in porometers.
It is a still further object of the invention to provide a novel technique and equipment for controlling the flow of air through a porometer.
It is a still further object of the invention to provide a precise technique for measuring the temperature of a leaf in a porometer.